Cycle notation...

of permutation groups.

I'm a little confused as what a question is asking... working in , it says to find a subgroup H that is generated by (123), (23), and (45) (written in cycle notation). Not sure what that means... from what I've learned of cycle notation, i thought (for example) the first would be:
1->1
2->2
3->3
4->4
5->5
and the second:
1->2
2->3
3->??
4->4
5->5
and the third:
1->4
2->5
3->3
4->1
5->2

but then i don't know how to 'generate' a group with these. my understanding is that a generator a produces elements of the subgroup ... but i don't know how to multiply these by themselves to produce new elements.